Logistic regression model of risk factors for severe asthma.^*

* OR denotes odds ratio, CI confidence interval. † Older (age 45 years and older) vs. young adult asthma (18–45 year old). ‡ OR per each year increase in asthma duration. Logistic regression model of risk factors for severe asthma.** OR指比值比（odds ratio），CI指置信区间（confidence interval）。 † 老年组（年龄≥45岁）与青年哮喘组（18~45岁）的对照。 ‡ 哮喘病程每增加1年对应的OR值。 * 重症哮喘危险因素的logistic回归模型。